1. Field of the Invention
The subject invention relates to antennas and more particularly to a multiple capacitor loaded antenna exhibiting high gain in tight packaging situations.
2. Description of Related Art
The single capacitor loaded monopole antenna is well-known in the prior art. Such an antenna may be visualized as two capacitor plates separated by a dielectric. The effective height of such an antenna is the distance between the plates. Hence, the range of the single monopole antenna of selected plate dimensions can only be increased by increasing the distance between the plates.
In certain applications where a flat or disc shaped antenna of relatively small thickness is required, the single capacitor loaded monopole antenna suggests itself for use. However, the antenna gain available with a single monopole antenna of the requisite small height confines its range to limits which are not practical.
Helical antennas are also known in the prior art and have been suggested for use in compact antennas. Such antennas employ a helical coil wherein gain is achieved by addition of signals in adjacent loops of the helix. See, e.g., U.S. Pat. Nos. 4,121,218 and 4,270,128. Because of their length, helical antennas again are not practical where a flat or disc shaped antenna of small thickness is needed.
Thus, the prior art has lacked an antenna which can provide the gain desired in applications with restrictive packaging requirements, especially those with thin, flat packages. It has appeared to the inventor that adjacent monopole elements could provide additional gain in such an environment. However, no technique of additively coupling such elements has been available. In addition, prior theory has suggested that such additive coupling could not achieve effective increases in antenna height because of predicted shunting out of E fields developed across the capacitive antenna elements.